Database Reference
In-Depth Information
Isis Wo od
Isis Ta vern
Flint Road
FIGURE 6.4
North of Isis Tavern?
to be careful; the “next to” that is a subproperty of the OGC property is grounded
in the GeoSPARQL query language and therefore has a precise implementation; the
other definition is entirely dependent on the users knowing the context in which it
has been applied. So, when we encounter a “next to” property, we need to check that
we understand its semantics: Is it grounded in a well-defined model such as RCC8 or
some less-rigorous context? Of course, it is better if the differences are explicitly rec-
ognized, so Merea Maps defines a separate property “neighbors” to implement this
less-precise property and uses it for their gazetteer. Merea Heritage in turn adopts
this property for its own use.
The “next to” property is of course just one of many that can exist in some impre-
cise form, some of which have RCC8 alternatives and some of which do not. They
can include “opposite,” “near,” and compass directions such as “north of.” It is always
necessary to be clear about the context in which these properties are used. If we con-
sider “near,” then this can be more or less precisely defined for a particular set of
circumstances; for instance, we can define “near” as meaning anything within 50 m.
The problem with “near” is that it is so context dependent that there can be dozens of
different definitions, each valid for a particular circumstance, our “next to” issue writ
large. Similarly, there can be problems with compass properties such as “north of,”
“south of,” and so on. Here, the problem is clear to see in Figure 6.4. Is the Isis Wood
to the north of the Isis Tavern? Yes, but parts clearly are not and are to the east, but
equally saying it is to the east is just as imprecise.
Of course, there is nothing to stop us saying
Isis Wood is north of Isis Tavern.
Isis Wood is east of Isis Tavern.
The point is that there are very many topological properties that are possible and
many different interpretations of these properties depending on the context, such
as we have seen with “near to.” One could decide that such properties are more
